Re: population sizes for colonising a planet

jdnicoll@xxxxxxxxx (James Nicoll) wrote:
>In article <4350C42C.F23291F4@xxxxxxx>, nyra <nyra@xxxxxxx> wrote:
>>
>>[1] my rough-guess figures - hopefully about correct to an order of
>>magnitude or two - are that 2 m² of Earth area receive the amount of
>>energy from the Sun that one human consumes.
>
> Rather surprisingly (Or at least _I_ was surprised when I realized
>this), human body produce about 100 watts and on average each square meter
>of the Earth gets about 350 watts, at least at the top of the atmosphere.
>So call it 1/3rd of a meter. 1% efficiency (which is even worse than photo-
>synthesis) would make that 30 square meters.
>
> There's a lot of room for improvement in the systems we use to
>turn daylight into thinking meat.

I think the efficiency is limited by the difficulty of extracting CO2 from its
microscopic atmospheric concentration. It may be why plants have leaves
rather than being giant flat sheets, and are more energy-efficient in dim and
diffuse light.

Solar panels look much more efficient at making electricity but if you then
had to turn that power into hydrocarbon fuel using CO2 and H2O as inputs I
have no idea if you could easily beat plants at their game.

-xx- Damien X-)
.